1. Field of the Invention
The present invention relates to a device provided with a structure reinforcing member (spacer) in a vacuum container, for example, an electron beam generation device for use in a display apparatus for displaying information such as characters and images, an image-forming apparatus such as an optical printer, and an electron microscope, and the like.
2. Related Background Art
Up to now, two types of electron sources, namely, a thermoelectron source and a cold cathode electron source have been known as electron-emitting devices. Examples of the cold cathode electron source include a field emission device (hereinafter referred to as FE device), a metal/insulator/metal device (hereinafter referred to as MIM device), and a surface conduction electron-emitting device (hereinafter referred to as SCE device).
For example, the surface conduction electron-emitting device has an advantage in that a large number of electron-emitting devices can be formed over a surface of a relatively large area because it is particularly simple in structure and easily manufactured among various cold cathode electron-emitting devices.
In addition, concerning an application of the surface conduction electron-emitting devices, for example, a display apparatus such as a display unit of a video camera or the like, a charged beam source, and the like have been studied.
In general, the above-mentioned display apparatus is provided with a vacuum container including a face plate and a rear plate which are provided to be opposed to each other, and a support frame which is provided so as to hermetically seal external peripheral portions of the face plate and the rear plate. In addition, the vacuum container has a spacer which is arranged in a space between the opposed rear plate and face plate.
A sufficient mechanical strength is required of the spacer in order to support the atmospheric pressure. The spacer should not affect significantly a trajectory of an electron flying between the rear plate and the face plate. Charging of the spacer is one of causes which affect the electron trajectory. It is considered that a part of electrons emitted from an electron source or an electron reflected by the face plate is incident in the spacer and a secondary electron is emitted from the spacer, or ions ionized by collision of electrons deposit on the surface of the spacer, with the result that the charging of the spacer occurs.
In the case in which the spacer is charged positively, since electrons flying in the vicinity of the spacer are attracted to the spacer, distortion occurs on a displayed image in the vicinity of the spacer. Such an influence due to the charging of the spacer becomes more conspicuous in accordance with increase in a space between the rear plate and the face plate.
As a countermeasure for preventing such charging of a spacer, a method of forming an electrode for correcting an electron trajectory in a spacer or removing charges by giving conductivity to a charged surface of the spacer and causing a faint electric current to flow to the spacer is possible.
Further, the method of giving conductivity to a charged surface of a spacer is applied to a spacer. JP 57-118355 A discloses a technique for coating a surface of a spacer with tin oxide. In addition, JP 03-49135 A discloses a technique for coating a surface of a spacer with a PdO glass material.
In addition, with a spacer electrode being provided in a contacting portion with a face plate or a rear plate, breakage of a spacer due to connection failure or concentration of electric currents can be prevented by applying an electric field to the above-mentioned coating material uniformly.
Moreover, EP 869528 discloses that a potential distribution in the vicinity of a spacer is controlled according to a shape of a spacer electrode and, as a result, a trajectory of electron beams can be controlled.
In the above-mentioned conventional examples, an electrode for correcting an electron trajectory in the spacer is formed or a high resistance film is formed on the surface of the spacer to neutralize positive charging, whereby charging can be relaxed to prevent electrons flying in the vicinity of a spacer from being attracted by the spacer.
However, charging may not be removed completely depending upon a device pitch, drive conditions, or the like, or it may be preferable not to give conductivity to a charged surface of a spacer taking into account mass production. Therefore, there have been demands for a satisfactory image display apparatus which can cope with such situations.